(Technical Field)
The present invention relates to a fault detection system that includes switches respectively provided to a pair of electric power lines connecting a DC power supply and electric equipment, and a determination section that determines whether or not a short-circuit fault has occurred in the switches.
(Related Art)
A fault detection system is known that includes a pair of electric power lines connecting between a DC power supply and electric equipment, relays provided to the electric power lines, a capacitor connected to the electric equipment in parallel, and a determination section that determines whether or not a short-circuit fault has occurred in switches in the relays (refer to Japanese Patent No. 3781289).
If the switch is stuck by melting, or a spring member in the relay or a drive circuit is failed, the switch may remain turned on even when the switch is controlled so as to be turned off. The determination section determines whether or not such a fault (short-circuit fault) has occurred.
The switches are respectively provided to the pair of electric power lines. When it is determined whether or not a short-circuit fault has occurred in the switches, only one of the pair of switches is controlled so as to be turned on. At this time, if a short-circuit fault has occurred in the other of the pair of switches, a current flows to the capacitor, whereby the voltage increases. Hence, determining whether or not the voltage has increased can determine whether or not a short-circuit fault has occurred in the other of the pair of switches. If it is determined that a short-circuit fault has not occurred, only the other of the pair of switches is controlled so as to be turned on. At this time, if a short-circuit fault has occurred in one of the pair of switches, a current flows to the capacitor, whereby the voltage increases. Hence, determining whether or not the voltage has increased can determine whether or not a short-circuit fault has occurred in the switch.
As described above, to check for occurrence of a short-circuit fault, the relays are required to be formed so that the pair of switches can be separately operated. That is, it is required to configure the fault detection system by providing two magnet coils in the relays so that the individual switches can be turned on and off by the individual magnet coils. Hence, the manufacturing cost of the relays increases.
Recently, it is considered that one magnet coil should be provided in the relay to turn on and off both of the pair of switches by the magnet coil, to decrease the manufacturing cost of the relay.
However, if one magnet coil is provided in the relay, the pair of switches cannot be separately operated. Hence, it cannot be determined whether or not a short-circuit fault has occurred in the switches.